AIN: anal intraepithelial neoplasia; can be graded as: 1, the least serious and similar to

LSIL; 2, more serious and akin to HSIL; or 3, the most serious; 2 and 3 indicate localized precancerous changes.

Joel Palefsky, MD, and Stephen Goldstone, MD, recommend high-resolution anoscopy for ASCUS, LSIL or HSIL, combined with biopsies of suspicious tissue, the results of which will determine treatment. (For more information on anal Paps, see “Smear Campaign,” POZ, August 1999.)